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A new single-dose vaccine against Rift Valley fever has shown promising results in livestock, paving the way for human trials later this year, researchers say.

Rift Valley fever — a mosquito-borne viral disease present in Africa and the Arabian Peninsula — mostly affects animals, but can also infect humans. At the moment, no vaccines are available for humans and “those widely used in livestock have major safety concerns”, scientists write in a paper published last month (5 February) in Scientific Reports.

“A large section of the genetic material in the chimpanzee adenovirus ChAd was deleted to prevent the virus from being able to reproduce in human or animals after vaccination.”

George Warimwe, University of Oxford’s Jenner Institute, United Kingdom

In trials carried out in Kenya and Saudi Arabia, they tested an experimental vaccine that could one day be used to treat both humans and livestock. It uses parts of a chimpanzee virus with a record of safe use in human and livestock vaccinations.

The vaccine also incorporates a gene for a Rift Valley fever virus protein, which is “recognised by the animal or human immune system, causing antibodies to be produced against the Rift Valley fever virus”, explains lead author George Warimwe, an immunologist at the University of Oxford’s Jenner Institute in the United Kingdom.

The researchers found that the vaccine is safe for humans and animals, and eliminated the Rift Valley fever virus from the blood.

“A large section of the genetic material in the chimpanzee adenovirus ChAd was deleted to prevent the virus from being able to reproduce in human or animals after vaccination, and the immune system rapidly clears the virus,” says Warimwe, who tested the vaccine in sheep, goats and cattle in Kenya.

In Saudi Arabia, the research team also tested the vaccine on camels, “which can transmit the virus to other animals without showing symptoms, and the results were positive with no side effects”, says coauthor Ayman El-Behiry, a microbiologist at Qassim University there.

Ahmed El-Sanousi, a virologist at Cairo University’s faculty of veterinary medicine in Egypt, praises the new vaccine for its low cost, ease of preparation and high safety.

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“The new technique can be used in an average laboratory, unlike [other vaccines] that need a highly equipped lab,” he says, adding that a similar approach could be used to develop vaccines against other infectious diseases such as malaria, tuberculosis and HIV/AIDS.

The next step will be human clinical trials later this year, Warimwe says. The team will also test the vaccine in livestock field trials in East Africa and seek licensing for veterinary use. Results from both trials are expected by the end of 2017, Warimwe adds.